Ternary compositions based on Bi(BB)O-3-PbTiO3-type compounds have been investigated for high-temperature piezoelectric applications. Compositions in the ternary were chosen to be near the binary morphotropic phase boundary (MPB) composition of BiScO3-PbTiO3 (BS-PT). Ternary compositions in (100-x-y)BiScO3-(x)Bi(Zr0.5Zn0.5)O-3-(y)PbTiO3 [(100-x-y)BS-xBZZ-yPT] have been investigated with x7.5. For compositions with x>10, the Curie temperature (T-C) decreased below 400 degrees C. Dielectric, piezoelectric, and electromechanical properties were characterized as a function of temperature, frequency, and electric field. Small additions of BZZ were shown to increase the electromechanical properties with only a small loss in T-C. The electromechanical properties were temperature stable up to the depoling temperature. The most promising composition exhibited a T-C of 430 degrees C, piezoelectric coefficient (d(33)) of 520pC/N, and a planar coupling factor (k(p)) of 0.45 that remained unchanged up to depoling temperature at 385 degrees C.